You sent survey invitations, the interface says they were sent, but participants report that nothing arrived. This article explains how sending works on LimeSurvey Cloud, what you can check yourself, and what to send us if the problem is on our side.

First: test emails vs. bulk invitations

A successful test email does not prove that bulk invitations work. Test emails and bulk invitations use different sending paths. Also, "sent successfully" in the interface does not guarantee delivery to the inbox.

So if your test email arrives but invitations do not, this is a known pattern — the checklist below helps narrow down the cause.

Checklist before contacting support

1. Ask recipients to check spam and quarantine folders. Company mail servers can quarantine bulk mail without notifying the recipient. Ask the recipient's IT team to whitelist the sender address.
2. Compare recipient domains. If some domains receive invitations and others never do, even though LimeSurvey shows OK status, the receiving domain is very likely filtering the mail. This must be fixed on the recipient's side (see step 1).
3. Check your own SMTP settings, if you use them. By default, LimeSurvey Cloud sends invitations through its own mail server, but you can route them through your own SMTP server instead. If you do, confirm the credentials and settings still work; see How do I configure email settings in LimeSurvey Cloud? for where to configure this.
4. Update authentication for Microsoft 365 / Outlook. Microsoft has deprecated Basic Authentication (username and password) for SMTP. Sending via O365 requires an OAuth-based setup.
5. Improve deliverability. See our article on how to ensure your email invitations avoid the spam folder (domain alignment, SPF/DKIM).

When it is on our side

If invitations are marked as sent but arrive nowhere — not in inboxes and not in spam — while test emails still work, the issue may be on the LimeSurvey Cloud platform, and our engineers can investigate the sending logs and fix it.

In that case, contact support and include:

1. Your survey ID.
2. When you sent the invitations.
3. Roughly how many invitations you sent.
4. Whether test emails work.
5. An example recipient email address that did not receive the invitation — sometimes the issue is on the receiving server.
6. A screenshot of any error, if there is one.

Support may ask for your written consent to access your account. Replying "I agree" is sufficient.

Self-hosted installations

This article covers LimeSurvey Cloud only. If you run the Community Edition on your own server, email delivery depends on your server and mail setup, and Cloud support cannot help with it. Instead:

• Check with your IT administrator.
• Ask the community at forums.limesurvey.org.
• Consult the LimeSurvey manual.